Tag Archives: control joints

There is a big problem with control joints or contraction joints. They are the saw cut joints we cut into concrete slabs to control cracking as the concrete cures. The problem is the floor owner typically wants the floor poured, joints cut, joints filled, and building occupied in 60 days or less. Concrete cures hard in typically 28 days, but it continues to shrink and crack for a about a year. The contraction joint that was 1/4″ when it was cut, can almost double in width in that first year leaving the 1/4″ of joint filler a bit short, cracked and generally a mess. The sidewalls of the joint are left unprotected and the joint spalling begins. You can replace all that gummy polyurea or brittle epoxy with Roadware 10 Minute Concrete Mender™ and leave your control joint problem behind.

Use Concrete Mender™ to repair cracks, joints and curling slabs under VCT or tile floors. The permanent performance and 10 minute cure turns this 2 day job into a one day (or one night) job. Keep business running with minimal down time.

Repairing contraction joints under VCT.

For spalled or failed control joints that are reflecting through the tile and the slabs are not curled, clean out the joints with a dust collecting diamond grinder.

Control or contraction joints repaired with 10 Minute Concrete Mender™ under VCT.

SPALLED CONTROL JOINT

(Fully cured non-moving)
1. Clean out with diamond grinder and remove dirt and dust. Score back spall with blade for a finished look.
2. Flood with Roadware 10 Minute Concrete Mender™
3. Add a fine graded silica sand and additional liquid to grade.
4. Strike off excess material and allow to cure for 10 minutes at 70°F.
5. Open to traffic. Finish and blend with a grinding stone if desired.

DELAMINATED SLAB

1. Drill hole into void.

2. Remove dust with a vacuum.

3. Flood with Roadware 10 Minute Concrete

Mender™ supplied in twin cartridges.

4. Add a fine graded silica sand and

additional liquid to fill holes to grade.

5. Strike off excess material and allow to

cure for 10 minutes at 70° F.

6. Open to traffic. Finish and blend with a

grinding stone if desired.

THRESHOLDS AND
UNEVEN SLABS

1. Clean out with diamond or wire grinder and remove dirt and dust. Score lower edge with diamond blade for a finished look.

Roadware Flexible Cement II™ is semi-ridged polyurethane for creating flexible bonds between concrete surfaces and other materials. This versatile material may also be used to protect contraction joints from traffic deterioration.

What is Flexible Cement II? ProprietaryPolyurethane Blend

Formulation: Classified

Manufacturing: South Saint Paul, Minnesota, USA

Origin: Designed for creating flexible bonds between concrete surfaces and dis-similur materials.

Function: To flow into concrete cracks and joints. Filling the void with a semi-flexible polyurethane the will accommodate heavy traffic.

Use Flexible Cement II™to repair cracks and protect control joints in parking structures, bridge decks, loading docks, and many types of structural concrete.

Control Joints

Use on industrial floors to protect saw-cut control joints from wheel traffic damage.

Cove joints

Use Flexible Cement II™ to seal cove joints where the floor meets a structural wall.

Electrical Podding

Seal electrical loops and embedded lighting systems.

Thresholds

Repair concrete thresholds with high thermal differentials.

Moisture

Flexible Cement II™ is tolerant of surface moisture when applied. Concrete should be as dry as practical to insure a good bond.

Concrete Bonding

Flexible Cement II™ is an excellent flexible adhesive for bonding metal, wood, and synthetic materials to concrete. Use to bond moldings and tack strips to concrete floors.

Bond asphalt to concrete.

Bond wood to concrete.

Bond metal to concrete.

Bond carpet nail strips to concrete.

Bond carpet molding to concrete.

High Traffic

Repairs are tough and can handle heavy industrial traffic.

Use Flexible Cement II™ to protect joints and cracks in concrete bridge decks and pavement where heavy traffic is anticipated. This polyurethane is about as hard as a roller blade wheel and will prevent debris from filling cracks and causing further deterioration of the concrete.

Flexible Cement II™ is recommended for low movement crack repair. This tough material will hold up to forklift and industrial traffic while allowing for some movement. For high movement areas and expansion joints, we recommend a softer caulk type material.

Question: How do you epoxy inject cracks in floor slabs on grade when you do not have access to the bottom of the slab? What keeps the product from running out the bottom and all over the place?Answer: We make these type of repairs all the time. The first thing to do is dump the epoxy. It is too thick, too brittle, and takes too long to set. Fast setting materials like 10 Minute Concrete Mender allow you to control set points deep in the crack and prevent material seepage.Roadware 10 Minute Concrete Mender™ has an ultra low viscosity of 8cps and will gravity inject into the smallest of cracks. We make the repair in stages adding fine silica sand into the crack as necessary to prevent the material from running out the bottom. The product can be injected with needle tip mixers as small as 18 gauge. With careful technique and experience you can make structural repair that will restore aggregate interlock and restore the slab.

Start out by adding a small amount Concrete Mender to the prepared crack and noting where material in running beyond the slab. Add a light dusting of silica sand or fine quartz to the crack and some more Concrete Mender. The Concrete Mender will combined with the particles of sand to form a quick setting, “mud” at the bottom of the crack. Repeat as necessary and repair the full depth of the slab.

This will be a structural repair with no ports, no pumps, and almost no down time.

Contraction joints (or control
joints) are joints cut into a slab shortly after pouring. The purpose of these joints is to control the cracking of the slab as it cures. Most concrete slabs shrink and sometimes curl for the first 12 months after pouring. Contraction joints allow the
slab to crack at pre-determined intervals instead of natural random cracking. Joint filler is used to protect the joints from spalling and chipping caused by traffic on the slab.

As the slab cures for the first
12 months, it shrinks in size and may even curl up at the joints. The contraction joints will expand as the slab shrinks. This causes the joint filler to split apart or dis-bond from the sides of the joint leaving them exposed to traffic.

When loads are rolled over the
joint. The force of the load has to transfer from the wheel, to the concrete, and to the base. If the slab is even slightly curled and the joint is expanded, the force of the load will impact on the joint causing cracking and spalling. You may even get stress cracking parallel to the joint. You can sometimes feel the uneven load transfer across the joint if you stand with one foot on either side of the joint and have someone else roll a heavy load across the joint.

Eventually, you get a spalled contraction joint. The joint filler has completely failed or is missing. Wheels go “thunk, thunk” every time they go over the joint. Productivity suffers, and the joint fills with dust and debris.

A popular and effective way to repair spalled contraction joints is to lock them back up with Roadware 10 Minute Concrete Mender™. Once the slab is 12 months old, the shrinkage and curling has finished. There is no longer a need for contraction joints. Now you can use Concrete Mender™ and silica sand to bond the slab back together from the base all the way up to
the top. This will stabilize the slab, restore aggregate interlock,
and allow for complete and even load transfer from the wheels all the way down to the base. Your contraction joint problems are solved.

NOTES: Locking up contraction joints
is recommended for interior controlled environment applications with sound concrete and base. Exterior applications may have different results. Always test a small section
of large repair for compatibility.